Combined sprocket and guide wheel



1937' A. w. NISBET COMBINED SPROCKET AND GUIDE WHEEL Filed Oct. 16, 1956 n-nva Inventor": Archibald W. Nisbeb, by ZVz uycl" His Attorney.

Patented Dec. 7, 1937 UNlTED STATES PATENT OFFIQE Archibald vW. Nisbet, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application October 1c, 1936, Serial No. 105,856

l. Claims.

In the manufacture of apparatus for generating, utilizing and conveying electricity, enormous quantities of textile fabric coated or impregnated with varnish or other compounds are used for insulating purposes. The fabric for such use requires in the manufacture thereof extreme care to prevent the formation of spots or areas of impaired dielectric strength. A special problem is presented in those coating machines in'which metallic conveyors are employed for moving the fabric within the machine while it is being cured. It has been found that the rubbing which takes place between metal sprocket teeth and metallic conveyor chains cause minute particles to be detached from the metal parts and deposited on the fabric where the varnish holds it fast. The distribution of the metal particles is greatly facilitated by the large volume of air which is being rapidly circulated within'the machine for the purpose of curing the coating. These metal particles, no matter how small or how few in number, result in a decrease of dielectric strength of the fabric. For some purposes as for example where very. high po tentials are involved, a fabric with only one or two minute particles of metal in a limited area would be worthless as an insulating material. For other and less exacting requirements, the material could be used provided the particles were not in alignment. As a general-proposition, it may be stated that it is not safe from an electrical standpoint to use any insulating fabric which contains even the slightest trace of metal.

The chain used with the conveyor of one type of coating machine with which I am familiar-is very long, the distance between centers of the sprockets meshing with the chain being of the order of eighty-five feet. Between sprockets, the

chain has to be supported for practically its en-.

tire length with the result that the friction load is a heavy one to which hasto. be added the load due to the weight of the coated fabric, all of which means that the loadand hence the wear on the chain and sprocket teeth is pronounced and hence replacements are required from time to time.

Experience has demonstrated that where sprockets of conventional design'are employed, the friction between the relatively movable parts o results in metallic dust. If the chain is harder than the material of the sprocket, most of the dust will be due to' wear on the sprocket. 'On the other hand, if the sprocket is made of harder material than the chain, most of the wear will -be .onthe chain. In bothcases, contamination results. To replace either the sprockets or the chain, especially the latter, involves shutting down the machine for a considerable period of time which seriously interferes with production and also involves a substantial expense.

My invention has for its object toprevent the formation and hence the distribution of metallic particles within fabric coating machines. Specifically, my invention is directed to the provision in a coating machine of a sprocket wheel having a body, portions of which act as guiding means for the conveyor chain, and removable nonmetallic inserts so that as the teeth become worn, they may be quickly replaced at a small expense and with only a limited shut down of the coating machine.

For a consideration of what I believe to be novel and my invention, attention is directed to theaccompanying description and claims appended thereto.

Fig. 1 is a plan view of a chain conveyor and sprockets; Fig. 2 is a plan view of a combined sprocket and guide wheel; Fig. 3 is an edge view of said Wheel; Fig. 4 is a plan View of the body of the wheel; Fig. 5 is a perspective view of one of the sprocket inserts; Fig. 6 is a cross-sectional view of one of the guides for the chain conveyor, and Fig. 7 is a detail view showing a means whereby the radial position of the teeth may be changed or adjusted.

l and 3 indicate combined sprocket and guide wheels, 9 the vertical supporting shafts therefor, and II] the chain conveyor moved by the wheels.

Each wheel comprises a metal body II having radial slots l2, the side walls of which are parallel to each other and at right angles to the bottom wall. The body is also provided with a circumferential groove it into which project the horizontally disposed links M, of the chain conveyor. The body is also provided with cutaway segmental portions l5 opening on one side which register with the downwardly extending hangers l6 which are welded or otherwise secured to the vertically disposed links ll of the chain conveyor. The material to be treated in the coating machineis suspended by one edge from the hangers. The hangers are so arranged that as the chain is moved by the wheels, they occupy a mid-position between the sprocket teeth. As will be seen, particularly from Fig. 4, there are four of these cut-away portions, that is to say, half the number of sprocket teeth. Their pitch depends upon the spacing of the hangers It. To the top and bottom faces of the body are secured fiatplates l8 and I9 which are held in place by numerous removable bolts 20. The center of the body and plates are bored to receive a shaft and are slotted to receive a driving key.

In Fig. 5 is shown one of the members or inserts in which the sprocket teeth 2 i of which there are eight, are formed. Each member or insert is made of non-metallic material such as canvas or duck arranged in layers with the fibres of which it is composed held in a highly compressed state by means of a heat-hardened binder, such as a phenolic condensation product. The body of each member or insert is of such size that it snugly fits the side walls of the radial slot [2 in the metal body H and rests on the bottom wall thereof. The member or insert has opposed projections 22 forming teeth which engage the ends of adjacent vertically disposed links I! of the chain, the bodies of said links fitting into the rounded cut-away portions 23. To provide for the horizontally disposed links, the member or insert has a groove or recess 24 which registers with the circumferential groove H3 in the metal body H. The members or inserts are held in place by the walls of the slots l2 which, being in contact therewith, take the load as the wheel turns and moves the chain conveyor. Each tooth is held in place against radial outward movement by one or more bolts 25 which pass through the top and bottom plates I 8 and IS.

The members or inserts may be cut to size from sheet stock and the tooth and groove therein formed by suitable machine operations.

It will be noted that the teeth are quite widely spaced so that instead of providing an insert for each link of the chain, there is one tooth for each three links. The cylindrical portion of body ll between the teeth in the present illustration is smooth'and takes no part in the transmission of power but the peripheral surfaces above and below the peripheral groove I3 act as guiding surfaces for the upper and lower parts of the vertical links I! as the chain travels and also prevent the links from twisting, while the groove I3 is of sumcient size freely to receive the innerparts of the horizontal links. It is to be noted that the arc of each guiding portion of the body H measured on the pitch circle is substantially greater than the are covered by each tooth member and its receiving slot.

In Fig. 6 is shown in section a guide and support for the chain conveyor between the wheels and comprising frame bars 21 to which are secured nonmetallic liners 28 that are or may be of the same material as the inserts and teeth of the wheel and upon which the horizontally disposed links of the chain move. Such an arrangement assists in preventing the formation of metal dust.

In the prior construction where the sprocket wheel was of usual construction and had integral metal teeth, much trouble, delay and expense was involved whenever they had to be replaced. The chain in these coating machines is kept taut by means of a weight acting on one of the wheel shafts 9 to pull it away from the other shaft. Such weights may be of the order of 250 pounds. To make a replacement, the weight has to be disconnected or blocked up, a substantial amount of slack provided in the chain to free all of the links from the sprocket teeth, wheel removed, a new one substituted and the parts restored to normal relation. With my improved construction, the advantage is obtained that the wheel body does not have to be disturbed on its shaft, thereby saving in labor and expense, and less trouble is eX- perienced in getting at the wheels. The inserts,

with their worn chain engaging teeth, can be removed one at a time and replaced merely by removing and replacing one bolt 25 for each block. Furthermore, the inserts can be adjusted radially by inserting thin fiat shims 26 between the base thereof and the bottom wall of the slot. For this purpose, the holes in the inserts are made slightly larger than the securing bolts 25. The effect of moving the inserts outwardly is to compensate for wear on the teeth, a wear which is not sufiicient to justify replacement. The fact that the wearing is confined to nonmetallic parts eliminates all trouble incident to the formation of metallic dust and its distribution throughout the coating machine by the circulating air where its deposit on dried or partly dried surfaces would seriously injure the fabric as an insulating agent.

With sprocket wheels of conventional design mounted on vertical shafts and the connecting chain traveling in the same horizontal plane as the wheels, it is necessary in order to ensure the proper release of the links from the teeth to use idlers or equivalent means to guide the chain as it leaves the driven sprocket. Due to the relatively wide spacing or pitch of the teeth of my improved sprocket with the intervening guide surfaces, the additional advantage is obtained that the teeth and links will freely release themselves without the use of idlers or equivalent devices.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A combined sprocket and guide wheel comprising a body having widely spaced radially extending open ended rectangular slots therein having parallel sides and cylindrical portions between the slots which cover a greater are of the circumference of the body than the slots and form guide surfaces for a co-operating chain, a nonmetallic member having parallel sides filling each of the slots and having a circumferential groove and a chain engaging tooth formed therein, parts of which are located on opposite sides of the groove, said tooth projecting radially outward by a sufficient amount to hold the co-operating chain out of contact with the body, and means for rigidly securing the members to the body.

2. A combined sprocket and guide wheel comprising a body having widely spaced radially extending open ended slots therein having parallel sides and cylindrical portions between the slots which cover a greater are of the circumference of the body than the slots and form guide surfaces for a cooperating chain, said portions having parts of a circumferentially extending chain link, receiving groove, a nonmetallic member having parallel sides and filling each of the slots having a chain engaging tooth formed therein and a centrally disposed circumferentially extending groove registering at its ends with adjacent portions of the groove in the body, metal side plates which cover the body and the members, and means for rigidly uniting the metallic and nonmetallic parts.

3. A combined sprocket and guide wheel'comprising a metal body having radially extending open ended slots in its periphery, and cylindrical portions between the slots which cover a greater are of the circumference of the body than the slots and form guide surfaces, said portions containing parts of a circumferential groove, nonmetallic members each having a base located in and filling one of the slots and-a groove therein registering with the circumferential groove in the body, a tooth formed in each member for engagement with links of a chain, parts of the tooth being located on opposite sides of the groove, plates which cover the sides of the body and also the side faces of the nonmetallic members, and means which pass through the body, side plates and members for uniting them.

4. A combined sprocket and guide Wheel comprising a body having radially extending open ended slots in its periphery and cylindrical portions between the slots which cover a greater are of the body than the radial slots and form guide surfaces for a co-operating link chain, said portions having parts of a circumferential groove with a portion of one of the walls thereof cut away to afford space for a hanger carried by the chain, and removable members each comprising nonmetallic material and a binder holding it in compression, each of said members having a base located in and filling one of the slots and having a circumferentially extending groove therein registering with the groove in the body, and a tooth formed therein for engagement with the links of a chain, parts of said tooth being located on opposite sides of the groove, and means for rigidly securing the members to the body.

ARCHI'BALD W. NISBET. 

